A note on entropic force and brane cosmology

Recently Verlinde proposed that gravity is an entropic force caused by information changes when a material body moves away from the holographic screen. In this note we apply this argument to brane cosmology, and show that the cosmological equation can be derived from this holographic scenario.Comment: 5 pages, no figures;references adde

Sodium vacancy ordering and the co-existence of localized spins and itinerant charges in NaxCoO2

The sodium cobaltate family (NaxCoO2) is unique among transition metal oxides because the Co sits on a triangular lattice and its valence can be tuned over a wide range by varying the Na concentration x. Up to now detailed modeling of the rich phenomenology (which ranges from unconventional superconductivity to enhanced thermopower) has been hampered by the difficulty of controlling pure phases. We discovered that certain Na concentrations are specially stable and are associated with superlattice ordering of the Na clusters. This leads naturally to a picture of co-existence of localized spins and itinerant charge carriers. For x = 0.84 we found a remarkably small Fermi energy of 87 K. Our picture brings coherence to a variety of measurements ranging from NMR to optical to thermal transport. Our results also allow us to take the first step towards modeling the mysterious ``Curie-Weiss'' metal state at x = 0.71. We suggest the local moments may form a quantum spin liquid state and we propose experimental test of our hypothesis.Comment: 16 pages, 5 figure

Partition Function Zeros of a Restricted Potts Model on Lattice Strips and Effects of Boundary Conditions

We calculate the partition function $Z(G,Q,v)$ of the $Q$-state Potts model exactly for strips of the square and triangular lattices of various widths $L_y$ and arbitrarily great lengths $L_x$, with a variety of boundary conditions, and with $Q$ and $v$ restricted to satisfy conditions corresponding to the ferromagnetic phase transition on the associated two-dimensional lattices. From these calculations, in the limit $L_x \to \infty$, we determine the continuous accumulation loci ${\cal B}$ of the partition function zeros in the $v$ and $Q$ planes. Strips of the honeycomb lattice are also considered. We discuss some general features of these loci.Comment: 12 pages, 12 figure

Addressing decision making for remanufacturing operations and design-for-remanufacture

Remanufacturing is a process of returning a used product to at least original equipment manufacturer original performance specification from the customers' perspective and giving the resultant product a warranty that is at least equal to that of a newly manufactured equivalent. This paper explains the need to combine ecological concerns and economic growth and the significance of remanufacturing in this. Using the experience of an international aero-engine manufacturer it discusses the impact of the need for sustainable manufacturing on organisational business models. It explains some key decision-making issues that hinder remanufacturing and suggests effective solutions. It presents a peer-validated, high-level design guideline to assist decision-making in design in order to support remanufacturing. The design guide was developed in the UK through the analysis of selections of products during case studies and workshops involving remanufacturing and conventional manufacturing practitioners as well as academics. It is one of the initial stages in the development of a robust design for remanufacture guideline

Design method of fabric formed concrete beams reinforced with W-FRP

Flexible moulds as external formwork and a novel robotically fabricated reinforcement, Wound FRP (W-FRP), provide the solution for the manufacture of complex structural concrete components being optimised to minimise material use and further reduce the carbon emissions from constructional industry. However, previous research has shown that the non-prismatic geometries and linear-elastic reinforcement could result in very different structural behaviours from the traditional concrete beams and invalidity of the existing codified design approaches. This research proposes revisions to the empirical equation to calculate the tensile force of inclined flexural reinforcement and a design method to predict the shear capacity of the W-FRP reinforced non-prismatic beams based on Modified Compression Field Theory (MCFT). A full-scale test of fabric formed T beam reinforced with W-FRP was conducted to demonstrate the validity of this new design approach. The research in this paper shows that: 1) the invalidity of the codified design approach could be attributed to the empirical calibration with prismatic beams; 2) geometry of the beam and the W-FRP shear reinforcement ratio are the main factors influence the flexural bar force development and 3) the proposed equation for calculating tensile force of flexural reinforcement could accurately predict the force development. This research provides a practical and valid approach for the future design of non-prismatic beams reinforced with W-FRP and addresses technical challenges in the way to minimising material use in concrete structures

Black Holes and Photons with Entropic Force

We study entropic force effects on black holes and photons. We find that application of an entropic analysis restricts the radial change $\Delta R$ of a black hole of radius $R_{\mathrm{H}}$, due to a test particle of a Schwartzchild radius $R_{h}$ moving towards the black hole by $\Delta x$ near black body surface, to be given by a relation $R_{\mathrm{H}} \Delta R= R_h \Delta x/2$, or {\Delta R}/{\lambdabar_M} = {\Delta x}/{2 \lambdabar_m}. We suggest a new rule regarding entropy changes in different dimensions, \Delta S= 2\pi k D \Delta l /\lambdabar, which unifies Verlinde's conjecture and the black hole entropy formula. We also propose to extend the entropic force idea to massless particles such as a photon. We find that there is an entropic force on a photon of energy $E_\gamma$, with $F=G M m_{\gamma}/R^2$, and therefore the photon has an effective gravitational mass $m_\gamma = E_\gamma/c^2$.Comment: 4 Latex pages, no figure